1. Field of the Invention
The present invention relates to a slave station receiving a control signal from a control section and transmitting a monitoring signal thereto via common data signal lines. A plurality of slave stations are connected in parallel to the common data signal lines, and a master station in the control section is connected to the common data signal lines.
2. Description of the Related Art
A picking system may control directions for an operation of receiving a necessary component to assemble a product from components stored in a storage rack, and for an operation of resupplying a component to the storage rack. In the picking system, a slave station terminal is used for the directions for receiving and resupplying a component. More specifically, the slave station can show that a component is stored in the storage rack and comprises an input device for notification information indicating that the component has been taken out. The slave station is arranged on each of a plurality of storage racks. The slave stations are connected to a main computer via a control unit. The main computer transmits a direction for receiving a component to the control unit. The control unit activates a lamp or an indicator provided to the storage rack on which the component to be received is placed to show the receiving direction. An operator who completes the receipt of the specified component operates a switch lever on the slave station in order to input the completion. The operation signal is received by the main computer via the control unit to monitor the process, prevent mistakes, resupply a component to the storage rack, as well as to control the number of stocks and order the supplies.
The switch lever of the slave station used by the picking system is preferably a switch lever tiltable to any directions considering user-friendliness. A variety of techniques have been proposed to improve the operability of the switch lever. The inventors proposed a contactless ON/OFF switch disclosed in JP2009-26509A. The contactless ON/OFF switch comprises a switch lever that is excellent in user-friendliness. The contactless ON/OFF switch comprises a cylindrical member that has flexibility and stretchability and thus may be freely restored to the normal position. The contactless ON/OFF switch also comprises a base member and a rod member that has flexibility. A first end of the cylindrical member is fixed to the base member. The rod member is inserted into the cylindrical member. A first end of the rod member is fixed to an end portion of the cylindrical member that is not fixed to the base member. A second end of the rod member is protruded from the cylindrical member. When a bending force is applied to the free end (the end portion fixed to the first end of the rod member) of the cylindrical member, the cylindrical member and the rod member are bent. As a result, the end portion (the moving end portion) of the rod member protruded from the cylindrical member is moved toward the free end along the shaft line of the rod member or is tilted from the shaft line. The movement of the moving end portion of the rod member is the same regardless of the direction of the bending force applied to the free end. Thus, if the movement of the end portion is converted to electrical signal binary and is output, the same output can be obtained independent of the direction in which the free end is bent, that is, the ON/OFF operation can be provided.
The inventors further proposed a structure of a switch lever for a contactless ON/OFF switch, the structure being disclosed in JP2010-123320A. The structure of the switch lever comprises a cylindrical member that has flexibility and stretchability and thus may be freely restored to the normal position. A first end of a rod member is inserted into the cylindrical member and fixed therein. A mirror surface is formed at an end of the rod member that is surrounded by the cylindrical member. A detecting portion is opposed to the mirror surface. The amount of light on a light-receiving element is changed by a slant of the mirror surface formed at the end of the rod member. The detecting portion detects the change based on the amount of light received by the light-receiving element during startup. Namely, the detecting portion resets the standard detection level at every startup. This reduces the affect of the aged deterioration of the mirror surface, thereby improving the durability of the switch lever. The structure can thus keep the operability that the switch lever can be tilted in any directions, while decreasing the frequency of breakdowns and thus decreasing care and costs required for maintenance.    Patent Literature 1: JP2009-26509A    Patent Literature 2: JP2010-123320A